比如我创建一个Kotlin Object类：ObjectMethod
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package com.baichuan.example.unit_testobject ObjectMethod { fun doSomething() { println("this is ObjectMethod#doSomething") } @JvmStatic fun doSomethingWithJvmStatic() { println("this is ObjectMethod#doSomethingWithJvmStatic") }} |
如果我直接去mock该类的doSomething方法，会报错。
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@Test@DisplayName("mock普通的kotlin静态方法")fun testMockKotlinObject() { Assertions.assertThrows(MissingMethodInvocationException::class.java) { Mockito.mockStatic(ObjectMethod::class.java).`when`<Unit>( ObjectMethod::doSomething ).thenAnswer { println("this is mocked Object#doSomething") } } ObjectMethod.doSomething()} |
这是因为kotlin里的object类里的方法虽然在kotlin里从形态跟使用上来看与静态方法无二。但是编译成java代码后，其本质其实是内部初始化了一个当前类的静态常量实例INSTANCE。这个INSTANCE在kotlin语法里被隐藏了，但在java里依然可以显示访问。ObjectMethod编译成java后的代码如下：
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public final class ObjectMethod { @NotNull public static final ObjectMethod INSTANCE = new ObjectMethod(); private ObjectMethod() { } public final void doSomething() { String var1 = "this is ObjectMethod#doSomething"; boolean var2 = false; System.out.println(var1); } @JvmStatic public static final void doSomethingWithJvmStatic() { String var0 = "this is ObjectMethod#doSomethingWithJvmStatic"; boolean var1 = false; System.out.println(var0); }} |
所以，不能mock ObjectMethod#doSomething本质上的原因是正常手段无法mock静态常量。如果想要使kotlin的object类中的方法能够被mock，只需在方法上加上@JvmStatic注解即可。被其标注的方法会被编译成普通的java静态方法。
上面说正常手段无法mock静态常量，那么非正常手段呢？其实这个非正常手段就是通过反射将被mock过的实例注入到ObjectMethod中即可。
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@Test@DisplayName("通过反射修改静态常量来mock普通的kotlin静态方法")fun testMockKotlinObjectMethodByReflection() { val mock = Mockito.mock(ObjectMethod::class.java) Mockito.`when`(mock.doSomething()).then { print("this is mocked ObjectMethod by reflection") } val declaredMethod = ObjectMethod::class.java.getDeclaredField("INSTANCE") ReflectionUtils.setFinalStatic(declaredMethod, mock) ObjectMethod.doSomething()} |
ReflectionUtils
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package com.baichuan.example.unit_testimport java.lang.reflect.Fieldimport java.lang.reflect.Modifierobject ReflectionUtils { @Throws(Exception::class) fun setFinalStatic(field: Field, newValue: Any) { field.isAccessible = true val modifiersField: Field = Field::class.java.getDeclaredField("modifiers") modifiersField.isAccessible = true modifiersField.setInt(field, field.modifiers and Modifier.FINAL.inv()) field.set(null, newValue) }} |
github
https://github.com/scientificCommunity/blog-sample/tree/main/unit-test-sample
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原文链接：https://blog.csdn.net/scientificCommunity/article/details/120258224
